1. Field of the Invention
The present invention is in the field of training apparatus, and specifically relates to apparatus for training technicians in the use of an ion chamber radiation detector while avoiding the use of radioactive material.
2. The Prior Art
In the present invention, the student holds an instrument which simulates an ion chamber and that includes a meter on which the intensity of the radiation is displayed. The instrument held by the student is not a functioning ion chamber, because that would necessitate the use of radioactive materials. Instead, the instrument held by the student includes a radio receiver. The radio receiver receives a signal that is sent by a radio transmitter that is controlled by the instructor. The instructor's transmitter has controls that the instructor manipulates to alter the amount and type of radiation simulated by altering the transmitted signal as the student moves about.
In U.S. Pat. No. 3,636,641, Daskam shows a receiver instrument in which an output signal is produced which is proportional to the signal strength received from the transmitter. Because the signal strength at a particular location is affected by surrounding objects, the signal received by the student's instrument is not entirely under the control of the instructor.
The systems shown in U.S. Pat. No. 3,276,143 of Jaquiss and U.S. Pat. No. 3,293,777 of Shaw, et al. are somewhat similar. Both of these patents show the use of radio transmitters that use directional antennas to produce an elongated field strength pattern, which simulates a possible radiation fallout pattern. In addition, hotspot transmitters are located within the primary radiation pattern. These systems rely on the fall-off of field strength to represent the manner in which the radio-activity diminishes with distance from the various sources. Once the apparatus has been set up, there appears to be minimal change introduced by the instructor, and the students are basically engaged in mapping the field strength of the radio signals (i.e., the antenna pattern).
Two other patents, namely U.S. Pat. No. 3,208,159 of Filipov and U.S. Pat. No. 2,900,740 of Brault, et al. show systems which work on a completely different principle from the patents discussed above. In these patents, a phosphor in powdered form is used to simulate radioactive material. The phosphor is illuminated by an instrument carried by the student, and the phosphor fluoresces at a different wavelength that is detected by an optical detector in the student's instrument. The concentration of the phosphor determines the strength of the signal displayed on the instrument. Unlike the inventions of these two patents, the present invention does not require the use of a phosphor.
The inventions in the above patents may all be characterized as operating on an analog principle, in which the magnitude of some physical variable is measured and displayed on the instrument carried by the student. The magnitude of the physical variable is not entirely under the instructor's control, and in some instances this can lead to an unrealistic simulation. As will be seen below, the present invention operates on a different principle, which permits a more direct control by the instructor, and a higher degree of realism.